US10335230B2 - Systems for thermal-feedback-controlled rate of fluid flow to fluid-cooled antenna assembly and methods of directing energy to tissue using same - Google Patents

Abstract

A method of directing energy to tissue using a fluid-cooled antenna assembly includes the initial step of providing an energy applicator. The energy applicator includes an antenna assembly and a hub providing at least one coolant connection to the energy applicator. The method also includes the steps of providing a coolant supply system including a fluid-flow path fluidly-coupled to the hub for providing fluid flow to the energy applicator, positioning the energy applicator in tissue for the delivery of energy to tissue when the antenna assembly is energized, and providing a thermal-feedback-controlled rate of fluid flow to the antenna assembly when energized using a feedback control system operably-coupled to a flow-control device disposed in fluid communication with the fluid-flow path.

Description

BACKGROUND

1. Technical Field

The present disclosure relates to electrosurgical devices and, more particularly, to systems for thermal-feedback-controlled rate of fluid flow to a fluid-cooled antenna assembly and methods of directing energy to tissue using the same.

2. Discussion of Related Art

Treatment of certain diseases requires the destruction of malignant tissue growths, e.g., tumors. Electromagnetic radiation can be used to heat and destroy tumor cells. Treatment may involve inserting ablation probes into tissues where cancerous tumors have been identified. Once the probes are positioned, electromagnetic energy is passed through the probes into surrounding tissue.

In the treatment of diseases such as cancer, certain types of tumor cells have been found to denature at elevated temperatures that are slightly lower than temperatures normally injurious to healthy cells. Known treatment methods, such as hyperthermia therapy, heat diseased cells to temperatures above 41° C. while maintaining adjacent healthy cells below the temperature at which irreversible cell destruction occurs. These methods involve applying electromagnetic radiation to heat, ablate and/or coagulate tissue. Microwave energy is sometimes utilized to perform these methods. Other procedures utilizing electromagnetic radiation to heat tissue also include coagulation, cutting and/or ablation of tissue.

Electrosurgical devices utilizing electromagnetic radiation have been developed for a variety of uses and applications. A number of devices are available that can be used to provide high bursts of energy for short periods of time to achieve cutting and coagulative effects on various tissues. There are a number of different types of apparatus that can be used to perform ablation procedures. Typically, microwave apparatus for use in ablation procedures include a microwave generator that functions as an energy source, and a microwave surgical instrument (e.g., microwave ablation probe) having an antenna assembly for directing the energy to the target tissue. The microwave generator and surgical instrument are typically operatively-coupled by a cable assembly having a plurality of conductors for transmitting microwave energy from the generator to the instrument, and for communicating control, feedback and identification signals between the instrument and the generator.

There are several types of microwave probes in use, e.g., monopole, dipole and helical, which may be used in tissue ablation applications. In monopole and dipole antenna assemblies, microwave energy generally radiates perpendicularly away from the axis of the conductor. Monopole antenna assemblies typically include a single, elongated conductor. A typical dipole antenna assembly includes two elongated conductors, which are linearly aligned and positioned end-to-end relative to one another with an electrical insulator placed therebetween. Helical antenna assemblies include a helically-shaped conductor that can be formed in various configurations. The main modes of operation of a helical antenna assembly are normal mode (broadside), in which the field radiated by the helix is maximum in a perpendicular plane to the helix axis, and axial mode (end fire), in which maximum radiation is along the helix axis.

A microwave transmission line typically includes a thin inner conductor that extends along the longitudinal axis of the transmission line and is surrounded by a dielectric material and is further surrounded by an outer conductor around the dielectric material such that the outer conductor also extends along the transmission line axis. In one variation of an antenna, a waveguiding structure, such as a length of transmission line or coaxial cable, is provided with a plurality of openings through which energy “leaks” or radiates away from the guiding structure. This type of construction is typically referred to as a “leaky coaxial” or “leaky wave” antenna.

Because of the small temperature difference between the temperature required for denaturing malignant cells and the temperature normally injurious to healthy cells, a known heating pattern and precise temperature control is needed to lead to more predictable temperature distribution to eradicate the tumor cells while minimizing the damage to surrounding normal tissue. Excessive temperatures can cause adverse tissue effects. During the course of heating, tissue in an overly-heated area may become desiccated and charred. As tissue temperature increases to 100° C., tissue will lose water content due to evaporation or by the diffusion of liquid water from treated cells, and the tissue becomes desiccated. This desiccation of the tissue changes the electrical and other material properties of the tissue, and may impede treatment. For example, as the tissue is desiccated, the electrical resistance of the tissue increases, making it increasingly more difficult to supply power to the tissue. Desiccated tissue may also adhere to the device, hindering delivery of power. At tissue temperatures in excess of 100° C., the solid contents of the tissue begin to char. Like desiccated tissue, charred tissue is relatively high in resistance to current and may impede treatment.

Microwave ablation probes may utilize fluid circulation to cool thermally-active components and dielectrically load the antenna radiating section. During operation of a microwave ablation device, if proper cooling is not maintained, e.g., flow of coolant fluid is interrupted or otherwise insufficient to cool device components sensitive to thermal failure, the ablation device may be susceptible to rapid failures due to the heat generated from the increased reflected power. In such cases, the time to failure is dependent on the power delivered to the antenna assembly and the duration and degree to which coolant flow is reduced or interrupted.

Cooling the ablation probe may enhance the overall heating pattern of the antenna, prevent damage to the antenna and prevent harm to the clinician or patient. During some procedures, the amount of cooling may not be sufficient to prevent excessive heating and resultant adverse tissue effects. Some systems for cooling an ablation device may allow the ablation device to be over-cooled, such as when the device is operating at low power settings. Over-cooling may prevent proper treatment or otherwise impede device tissue effect by removing thermal energy from the targeted ablation site.

SUMMARY

The present disclosure relates to an electrosurgical system including an electrosurgical device adapted to direct energy to tissue, one or more temperature sensors associated with the electrosurgical device, a fluid-flow path leading to the electrosurgical device, and a flow-control device disposed in fluid communication with the fluid-flow path. The system also includes a processor unit communicatively-coupled to the one or more temperature sensors and communicatively-coupled to the flow-control device. The processor unit is configured to control the flow-control device based on determination of a desired fluid-flow rate using one or more electrical signals outputted from the one or more temperature sensors.

The present disclosure also relates to an electrosurgical system including an electrosurgical device adapted to direct energy to tissue and a coolant supply system adapted to provide coolant fluid to the electrosurgical device. The coolant supply system includes a coolant source, a first fluid-flow path fluidly-coupled to the electrosurgical device to provide fluid flow from the coolant source to the electrosurgical device, a second fluid-flow path fluidly-coupled to the electrosurgical device to provide fluid flow from the energy applicator to the coolant source, a third fluid-flow path fluidly-coupled to the first fluid-flow path and the second fluid-flow path, and a flow-control device disposed in fluid communication with the third fluid-flow path. The system also includes one or more temperature sensors associated with the electrosurgical device and a feedback control system adapted to provide a thermal-feedback-controlled rate of fluid flow to the electrosurgical device. The feedback control system includes a processor unit communicatively-coupled to the one or more temperature sensors and communicatively-coupled to the flow-control device. The processor unit is configured to control the flow-control device based on determination of a desired fluid-flow rate using one or more electrical signals outputted from the one or more temperature sensors.

The present disclosure also relates to a method of directing energy to tissue using a fluid-cooled antenna assembly including the initial step of providing an energy applicator. The energy applicator includes an antenna assembly and a hub providing at least one coolant connection to the energy applicator. The method also includes the steps of providing a coolant supply system including a fluid-flow path fluidly-coupled to the hub for providing fluid flow to the energy applicator, positioning the energy applicator in tissue for the delivery of energy to tissue when the antenna assembly is energized, and providing a thermal-feedback-controlled rate of fluid flow to the antenna assembly when energized using a feedback control system operably-coupled to a flow-control device disposed in fluid communication with the fluid-flow path.

The present disclosure also relates to a method of directing energy to tissue using a fluid-cooled antenna assembly including the initial steps of providing an energy applicator and a coolant supply system adapted to provide coolant fluid to the energy applicator. The energy applicator includes an antenna assembly and a coolant chamber adapted to circulate coolant fluid around at least a portion of the antenna assembly. The coolant chamber is fluidly-coupled to the coolant supply system. The method also includes the steps of positioning the energy applicator in tissue for the delivery of energy to tissue when the antenna assembly is energized, and providing a thermal-feedback-controlled rate of fluid flow to the antenna assembly when energized by using a feedback control system including a processor unit configured to control a flow-control device associated with the coolant supply system based on determination of a desired fluid-flow rate using one or more electrical signals outputted from one or more temperature sensors associated with the energy applicator.

BRIEF DESCRIPTION OF THE DRAWINGS

Objects and features of the presently-disclosed systems for thermal-feedback-controlled rate of fluid flow to a fluid-cooled antenna assembly and methods of directing energy to tissue using the same will become apparent to those of ordinary skill in the art when descriptions of various embodiments thereof are read with reference to the accompanying drawings, of which:

FIG. 1 is a schematic diagram of an electrosurgical system including an energy-delivery device and a feedback control system operably associated with a fluid supply system fluidly-coupled to the energy-delivery device in accordance with an embodiment of the present disclosure;

FIG. 2 is a schematic diagram of a feedback control system, such as the feedback control system ofFIG. 1, in accordance with an embodiment of the present disclosure;

FIG. 3 is a block diagram of an electrosurgical system including an embodiment of the electrosurgical power generating source ofFIG. 1 in accordance with the present disclosure;

FIG. 4 is a schematic diagram of an electrosurgical system including the energy-delivery device ofFIG. 1 shown with another embodiment of a feedback control system in operable connection with another embodiment of a fluid supply system in accordance with the present disclosure;

FIG. 5 is a schematic diagram of a feedback control system in accordance with another embodiment of the present disclosure;

FIG. 6 is a flowchart illustrating a method of directing energy to tissue using a fluid-cooled antenna assembly in accordance with an embodiment of the present disclosure; and

FIG. 7 is a flowchart illustrating a method of directing energy to tissue using a fluid-cooled antenna assembly in accordance with another embodiment of the present disclosure.

DETAILED DESCRIPTION

Hereinafter, embodiments of the presently-disclosed systems for thermal-feedback-controlled rate of fluid flow to a fluid-cooled antenna assembly and methods of directing energy to tissue using the same are described with reference to the accompanying drawings. Like reference numerals may refer to similar or identical elements throughout the description of the figures. As shown in the drawings and as used in this description, and as is traditional when referring to relative positioning on an object, the term “proximal” refers to that portion of the apparatus, or component thereof, closer to the user and the term “distal” refers to that portion of the apparatus, or component thereof, farther from the user.

This description may use the phrases “in an embodiment,” “in embodiments,” “in some embodiments,” or “in other embodiments,” which may each refer to one or more of the same or different embodiments in accordance with the present disclosure. For the purposes of this description, a phrase in the form “A/B” means A or B. For the purposes of the description, a phrase in the form “A and/or B” means “(A), (B), or (A and B)”. For the purposes of this description, a phrase in the form “at least one of A, B, or C” means “(A), (B), (C), (A and B), (A and C), (B and C), or (A, B and C)”.

Electromagnetic energy is generally classified by increasing energy or decreasing wavelength into radio waves, microwaves, infrared, visible light, ultraviolet, X-rays and gamma-rays. As it is used in this description, “microwave” generally refers to electromagnetic waves in the frequency range of 300 megahertz (MHz) (3×10⁸cycles/second) to 300 gigahertz (GHz) (3×10¹¹cycles/second).

As it is used in this description, “ablation procedure” generally refers to any ablation procedure, such as, for example, microwave ablation, radiofrequency (RF) ablation, or microwave or RF ablation-assisted resection. As it is used in this description, “energy applicator” generally refers to any device that can be used to transfer energy from a power generating source, such as a microwave or RF electrosurgical generator, to tissue. For the purposes herein, the term “energy-delivery device” is interchangeable with the term “energy applicator”. As it is used in this description, “transmission line” generally refers to any transmission medium that can be used for the propagation of signals from one point to another.

As it is used in this description, “fluid” generally refers to a liquid, a gas, a liquid containing a dissolved gas or dissolved gases, a mixture of gas and liquid, gas and suspended solids, liquid and suspended solids, or a mixture of gas, liquid and suspended solids. As it is used in this description, “rate of fluid flow” generally refers to volumetric flow rate. Volumetric flow rate may be defined as a measure of the volume of fluid passing a point in a system per unit time, e.g., cubic meters per second (m³s⁻¹) in SI units, or cubic feet per second (Cu ft/s). Generally speaking, volumetric fluid-flow rate can be calculated as the product of the cross-sectional area for flow and the flow velocity. In the context of mechanical valves, the fluid-flow rate, in the given through-flow direction, may be considered to be a function of the variable restriction geometry for a given flow passage configuration and pressure drop across the restriction. For the purposes herein, the term “fluid-flow rate” is interchangeable with the term “rate of fluid flow”.

As it is used in this description, “pressure sensor” generally refers to any pressure-sensing device capable of generating a signal representative of a pressure value. For the purposes herein, the term “pressure transducer” is interchangeable with the term “pressure sensor”.

As it is used herein, the term “computer” generally refers to anything that transforms information in a purposeful way. For the purposes of this description, the terms “software” and “code” should be interpreted as being applicable to software, firmware, or a combination of software and firmware. For the purposes of this description, “non-transitory” computer-readable media include all computer-readable media, with the sole exception being a transitory, propagating signal.

Various embodiments of the present disclosure provide systems for thermal-feedback-controlled rate of fluid flow to an electrosurgical device, such as an ablation probe including a fluid-cooled antenna assembly. Embodiments may be implemented using electromagnetic radiation at microwave frequencies or at other frequencies. An electrosurgical system including a coolant supply system and a feedback control system adapted to provide a thermal-feedback-controlled rate of fluid flow to an energy applicator, according to various embodiments, is designed and configured to operate between about 300 MHz and about 10 GHz. Systems for thermal-feedback-controlled rate of fluid flow to electrosurgical devices, as described herein, may be used in conjunction with various types of devices, such as microwave antenna assemblies having either a straight or looped radiating antenna portion, etc., which may be inserted into or placed adjacent to tissue to be treated.

Various embodiments of the presently-disclosed electrosurgical systems including a feedback control system adapted to provide a thermal-feedback-controlled rate of fluid flow to an energy applicator disposed in fluid communication with a coolant supply system are suitable for microwave ablation and for use to pre-coagulate tissue for microwave ablation-assisted surgical resection. Although various methods described hereinbelow are targeted toward microwave ablation and the complete destruction of target tissue, it is to be understood that methods for directing electromagnetic radiation may be used with other therapies in which the target tissue is partially destroyed or damaged, such as, for example, to prevent the conduction of electrical impulses within heart tissue. In addition, although the following description describes the use of a dipole microwave antenna, the teachings of the present disclosure may also apply to a monopole, helical, or other suitable type of antenna assembly.

FIG. 1 shows anelectrosurgical system10 according to an embodiment of the present disclosure that includes an energy applicator or probe100, an electrosurgicalpower generating source28, e.g., a microwave or RF electrosurgical generator, and afeedback control system14 operably associated with acoolant supply system11.Probe100 is operably-coupled to the electrosurgicalpower generating source28, and disposed in fluid communication with thecoolant supply system11. In some embodiments, one or more components of thecoolant supply system11 may be integrated fully or partially into the electrosurgicalpower generating source28.Coolant supply system11, which is described in more detail later in this description, is adapted to provide coolant fluid “F” to theprobe100.Probe100, which is described in more detail later in this description, may be integrally associated with ahub142 configured to provide electrical and/or coolant connections to the probe. In some embodiments, theprobe100 may extend from a handle assembly (not shown).

In some embodiments, theelectrosurgical system10 includes one or more sensors capable of generating a signal indicative of a temperature of a medium in contact therewith (referred to herein as temperature sensors) and/or one or more sensors capable of generating a signal indicative of a rate of fluid flow (referred to herein as flow sensors). In such embodiments, thefeedback control system14 may be adapted to provide a thermal-feedback-controlled rate of fluid flow to theprobe100 using one or more signals output from one or more temperature sensors and/or one or more flow sensors operably associated with theprobe100 and/or conduit fluidly-coupled to theprobe100.

An embodiment of a feedback control system, such as thefeedback control system14 ofFIG. 1, in accordance with the present disclosure, is shown in more detail inFIG. 2. It is to be understood, however, that other feedback control system embodiments (e.g.,feedback control systems414 and514 shown inFIGS. 4 and 5, respectively) may be used in conjunction with coolant supply systems in various configurations. In some embodiments, thefeedback control system14, or component(s) thereof, may be integrated fully or partially into the electrosurgicalpower generating source28.

In the embodiment shown inFIG. 1, thefeedback control system14 is operably associated with aprocessor unit82 disposed within or otherwise associated with the electrosurgicalpower generating source28.Processor unit82 may be communicatively-coupled to one or more components or modules of the electrosurgicalpower generating source28, e.g., auser interface121 and agenerator module86.Processor unit82 may additionally, or alternatively, be communicatively-coupled to one or more temperature sensors (e.g., two sensors “TS₁” and “TS₂” shown inFIG. 1) and/or one or more flow sensors (e.g., one sensor “FS₁” shown inFIG. 1) for receiving one or more signals indicative of a temperature (referred to herein as temperature data) and/or one or more signals indicative of a flow rate (referred to herein as flow data). Transmission lines may be provided to electrically couple the temperature sensors, flow sensors and/or other sensors, e.g., pressure sensors, to theprocessor unit82.

Feedback control system embodiments may additionally, or alternatively, be operably associated with a processor unit deployed in a standalone configuration, and/or a processor unit disposed within theprobe100 or otherwise associated therewith. In some embodiments, where theprobe100 extends from a handle assembly (not shown), the feedback control system may be operably associated with a processor unit disposed within the handle assembly. Examples of handle assembly embodiments are disclosed in commonly assigned U.S. patent application Ser. No. 12/686,726 filed on Jan. 13, 2010, entitled “ABLATION DEVICE WITH USER INTERFACE AT DEVICE HANDLE, SYSTEM INCLUDING SAME, AND METHOD OF ABLATING TISSUE USING SAME”.

Electrosurgicalpower generating source28 may include any generator suitable for use with electrosurgical devices, and may be configured to provide various frequencies of electromagnetic energy. In some embodiments, the electrosurgicalpower generating source28 is configured to provide microwave energy at an operational frequency from about 300 MHz to about 10 GHz. In some embodiments, the electrosurgicalpower generating source28 is configured to provide electrosurgical energy at an operational frequency from about 400 KHz to about 500 KHz. An embodiment of an electrosurgical power generating source, such as the electrosurgicalpower generating source28 ofFIG. 1, in accordance with the present disclosure, is shown in more detail inFIG. 3.

Probe100 may include one or more antennas of any suitable type, such as an antenna assembly (or antenna array) suitable for use in tissue ablation applications. For ease of explanation and understanding, theprobe100 is described as including asingle antenna assembly112. In some embodiments, theantenna assembly112 is substantially disposed within asheath138.Probe100 generally includes acoolant chamber137 defined about theantenna assembly112. In some embodiments, thecoolant chamber137, which is described in more detail later in this description, includes an interior lumen defined by thesheath138.

Probe100 may include afeedline110 coupled to theantenna assembly112. Atransmission line16 may be provided to electrically couple thefeedline110 to the electrosurgicalpower generating source28.Feedline110 may be coupled to aconnection hub142, which is described in more detail later in this description, to facilitate the flow of coolant and/or buffering fluid into, and out of, theprobe100.

In the embodiment shown inFIG. 1, thefeedback control system14 is operably associated with a flow-control device50 disposed in fluid communication with a fluid-flow path of the coolant supply system11 (e.g., first coolant path19) fluidly-coupled to theprobe100. Flow-control device50 may include any suitable device capable of regulating or controlling the rate of fluid flow passing though the flow-control device50, e.g., a valve of any suitable type operable to selectively impede or restrict flow of fluid through passages in the valve.Processor unit82 may be configured to control the flow-control device50 based on determination of a desired fluid-flow rate using temperature data received from one or more temperature sensors (e.g., “TS₁”, “TS₂” through “TS_N” shown inFIG. 2).

In some embodiments, the flow-control device50 includes avalve52 including avalve body54 and anelectromechanical actuator56 operatively-coupled to thevalve body54.Valve body54 may be implemented as a ball valve, gate valve, butterfly valve, plug valve, or any other suitable type of valve. In the embodiment shown inFIG. 1, theactuator56 is communicatively-coupled to theprocessor unit82 via atransmission line32.Processor unit82 may be configured to control the flow-control device50 by activating theactuator56 to selectively adjust the fluid-flow rate in a fluid-flow path (e.g.,first coolant path19 of the coolant supply system11) fluidly-coupled to theconnection hub142 to achieve a desired fluid-flow rate. The desired fluid-flow rate may be determined by a computer program and/or logic circuitry associated with theprocessor unit82. The desired fluid-flow rate may additionally, or alternatively, be selected from a look-up table “T_X,Y” (shown inFIGS. 2 and 5) or determined by a computer algorithm stored within a memory device8 (shown inFIGS. 2 and 5).

Embodiments including a suitable pressure-relief device40 disposed in fluid communication with thediversion flow path21 may allow the fluid-movement device60 to run at a substantially constant speed and/or under a near-constant load (head pressure) regardless of the selective adjustment of the fluid-flow rate in thefirst coolant path19. Utilizing a suitable pressure-relief device40 disposed in fluid communication with thediversion flow path21, in accordance with the present disclosure, may allow the fluid-movement device60 to be implemented as a single speed device, e.g., a single speed pump.

Feedback control system14 may utilize data “D” (e.g., data representative of a mapping of temperature data to settings for properly adjusting one or more operational parameters of the flow-control device50 to achieve a desired temperature and/or a desired ablation) stored in a look-up table “T_X,Y” (shown inFIGS. 2 and 5), where X denotes columns and Y denotes rows, or other data structure, to determine the desired fluid-flow rate. In the embodiment shown inFIG. 1, theelectrosurgical system10 includes a first temperature sensor “TS₁” capable of generating a signal indicative of a temperature of a medium in contact therewith and a second temperature sensor “TS₂” capable of generating a signal indicative of a temperature of a medium in contact therewith.Feedback control system14 may be configured to utilize signals received from the first temperature sensor “TS₁” and/or the second temperature sensor “TS₂” to control the flow-control device50.

In some embodiments, theelectrosurgical system10 includes a flow sensor “FS₁” communicatively-coupled to theprocessor unit82, e.g., via atransmission line36. In some embodiments, the flow sensor “FS₁” may be disposed in fluid communication with thefirst coolant path19 or thesecond coolant path20.Processor unit82 may be configured to control the flow-control device50 based on determination of a desired fluid-flow rate using one or more signals received from the flow sensor “FS₁”. In some embodiments, theprocessor unit82 may be configured to control the flow-control device50 based on determination of a desired fluid-flow rate using one or more signals received from the flow sensor “FS₁” in conjunction with one or more signals received from the first temperature sensor “TS₁” and/or the second temperature sensor “TS₂”. Although theelectrosurgical system10 shown inFIG. 1 includes one flow sensor “FS₁”, alternative embodiments may be implemented with a plurality of flow sensors (e.g., “FS₁”, “FS₂” through “FS_M” shown inFIG. 2) adapted to provide a measurement of the rate of fluid flow into and/or out of theprobe100 and/or conduit fluidly-coupled to theprobe100.

Electrosurgical system10 may additionally, or alternatively, include one or more pressure sensors (e.g., “PS₁”, “PS₂” through “PS_K” shown inFIG. 5) adapted to provide a measurement of the fluid pressure in theprobe100 and/or conduit fluidly-coupled to theprobe100. In some embodiments, theelectrosurgical system10 includes one or more pressure sensors (e.g., pressure sensor70) disposed in fluid communication with one or more fluid-flow paths (e.g., first coolant path19) of thecoolant supply system11 as opposed to a pressure sensor disposed within theprobe100, reducing cost and complexity of theprobe100.

In the embodiment shown inFIG. 1, theprocessor unit82 is operably associated with apressure sensor70 disposed in fluid communication with a fluid-flow path of thecoolant supply system11.Processor unit82 may be communicatively-coupled to thepressure sensor70 via atransmission line30 or wireless link.Processor unit82 may additionally, or alternatively, be operably associated with one or more pressure sensors disposed within theprobe100, e.g., disposed in fluid communication with thecoolant chamber137.

Pressure sensor70 may include any suitable type of pressure sensor, pressure transducer, pressure transmitter, or pressure switch. Pressure sensor70 (also referred to herein as “pressure transducer”) may include a variety of components, e.g., resistive elements, capacitive elements and/or piezo-resistive elements, and may be disposed at any suitable position in thecoolant supply system11. In some embodiments, thepressure transducer70 is disposed in fluid communication with thefirst coolant path19 located between the fluid-movement device60 and the flow-control device50, e.g., placed at or near the flow-control device50.

In some embodiments, theprocessor unit82 may be configured to control the flow-control device50 based on determination of a desired fluid-flow rate using pressure data received from one or more pressure sensors. In some embodiments, theprocessor unit82 may be configured to control the flow-control device50 based on determination of a desired fluid-flow rate using one or more signals received from the first temperature sensor “TS₁” and/or the second temperature sensor “TS₂” and/or the flow sensor “FS₁” in conjunction with one or more signals received from thepressure transducer70.

In some embodiments, theprocessor unit82 may be configured to control the amount of power delivered to theantenna assembly112 based on time and power settings provided by the user in conjunction with sensed temperature signals indicative of a temperature of a medium, e.g., coolant fluid “F”, in contact with one or one temperature sensors operably associated with theantenna assembly112 and/or theconnection hub142. In some embodiments, theprocessor unit82 may be configured to decrease the amount of power delivered to theantenna assembly112 when sensed temperature signals indicative of a temperature below a predetermined temperature threshold are received byprocessor unit82, e.g., over a predetermined time interval.

Processor unit82 may be configured to control one or more operating parameters associated with the electrosurgicalpower generating source28 based on determination of whether the pressure level of fluid in theprobe100 and/or conduit fluidly-coupled to theprobe100 is above a predetermined threshold using pressure data received from one or more pressure sensors, e.g.,pressure transducer70. Examples of operating parameters associated with the electrosurgicalpower generating source28 include without limitation temperature, impedance, power, current, voltage, mode of operation, and duration of application of electromagnetic energy.

In some embodiments, the output signal of thepressure transducer70, representing a pressure value and possibly amplified and/or conditioned by means of suitable components (not shown), is received by theprocessor unit82 and used for determination of whether the pressure level of fluid in theprobe100 and/or conduit fluidly-coupled to theprobe100 is above a predetermined threshold in order to control when power is delivered to theantenna assembly112. In some embodiments, in response to a determination that the pressure level of fluid in theprobe100 and/or conduit fluidly-coupled to theprobe100 is below the predetermined threshold, theprocessor unit82 may be configured to decrease the amount of power delivered to theantenna assembly112 and/or to stop energy delivery between the electrosurgicalpower generating source28 and theprobe100. In some embodiments, theprocessor unit82 may be configured to enable energy delivery between the electrosurgicalpower generating source28 and theprobe100 based on determination that the pressure level of fluid in theprobe100 and/or conduit fluidly-coupled to theprobe100 is above the predetermined threshold.

In some embodiments, thepressure transducer70 is adapted to output a predetermined signal to indicate a sensed pressure below that of the burst pressure of the pressure-relief device40. A computer program and/or logic circuitry associated with theprocessor unit82 may be configured to enable the electrosurgicalpower generating source28 and the flow-control device50 in response to a signal from thepressure transducer70. A computer program and/or logic circuitry associated with theprocessor unit82 may be configured to output a signal indicative of an error code and/or to activate anindicator unit129 if a certain amount of time elapses between the point at which energy delivery to theprobe100 is enabled and when the pressure signal is detected, e.g., to ensure that the fluid-movement device60 is turned on and/or that theprobe100 is receiving flow of fluid before theantenna assembly112 can be activated.

As shown inFIG. 1, afeedline110 couples theantenna assembly112 to aconnection hub142.Connection hub142 may have a variety of suitable shapes, e.g., cylindrical, rectangular, etc.Connection hub142 generally includes ahub body145 defining anoutlet fluid port177 and aninlet fluid port179.Hub body145 may include one or more branches, e.g., threebranches164,178 and176, extending from one or more portions of thehub body145. In some embodiments, one or more branches extending from thehub body145 may be configured to house one or more connectors and/or ports, e.g., to facilitate the flow of coolant and/or buffering fluid into, and out of, theconnection hub142.

In the embodiment shown inFIG. 1, thehub body145 includes afirst branch164 adapted to house acable connector165, asecond branch178 adapted to house theinlet fluid port179, and athird branch176 adapted to house theoutlet fluid port177. It is to be understood, however, that other connection hub embodiments may also be used. Examples of hub embodiments are disclosed in commonly assigned U.S. patent application Ser. No. 12/401,268 filed on Mar. 10, 2009, entitled “COOLED DIELECTRICALLY BUFFERED MICROWAVE DIPOLE ANTENNA”, and U.S. Pat. No. 7,311,703, entitled “DEVICES AND METHODS FOR COOLING MICROWAVE ANTENNAS”.

In some embodiments, the flow sensor “FS₁” is disposed in fluid communication with thefirst coolant path19, e.g., disposed within theinlet fluid port179 or otherwise associated with thesecond branch178, and the second temperature sensor “TS₂” is disposed in fluid communication with thesecond coolant path20, e.g., disposed within theoutlet fluid port177 or otherwise associated with thethird branch176. In other embodiments, the second temperature sensor “TS₂” may be disposed within theinlet fluid port179 or otherwise associated with thesecond branch178, and the flow sensor “FS₁” may be disposed within theoutlet fluid port177 or otherwise associated with thethird branch176.

Coolant supply system11 generally includes a substantially closed loop having afirst coolant path19 leading to theprobe100 and asecond coolant path20 leading from theprobe100, acoolant source90, and a fluid-movement device60, e.g., disposed in fluid communication with thefirst coolant path19. In some embodiments, thecoolant supply system11 includes a third coolant path21 (also referred to herein as a “diversion flow path”) disposed in fluid communication with thefirst coolant path19 and thesecond coolant path20. The conduit layouts of thefirst coolant path19,second coolant path20 andthird coolant path21 may be varied from the configuration depicted inFIG. 1.

In some embodiments, a pressure-relief device40 may be disposed in fluid communication with thediversion flow path21. Pressure-relief device40 may include any type of device, e.g., a spring-loaded pressure-relief valve, adapted to open at a predetermined set pressure and to flow a rated capacity at a specified over-pressure. In some embodiments, one or more flow-restrictor devices (not shown) suitable for preventing backflow of fluid into thefirst coolant path19 may be disposed in fluid communication with thediversion flow path21. Flow-restrictor devices may include a check valve or any other suitable type of unidirectional flow restrictor or backflow preventer, and may be disposed at any suitable position in thediversion flow path21 to prevent backflow of fluid from thediversion flow path21 into thefirst coolant path19.

In some embodiments, thefirst coolant path19 includes a firstcoolant supply line66 leading from thecoolant source90 to the fluid-movement device60, a secondcoolant supply line67 leading from the fluid-movement device60 to the flow-control device50, and a thirdcoolant supply line68 leading from the flow-control device50 to theinlet fluid port179 defined in thesecond branch178 of theconnection hub body145, and thesecond coolant path20 includes a firstcoolant return line95 leading from theoutlet fluid port177 defined in thethird branch176 of thehub body145 to thecoolant source90. Embodiments including thediversion flow path21 may include a secondcoolant return line94 fluidly-coupled to the secondcoolant supply line67 and the firstcoolant return line95. Pressure-relief device40 may be disposed at any suitable position in the secondcoolant return line94. The spacing and relative dimensions of coolant supply lines and coolant return lines may be varied from the configuration depicted inFIG. 1.

Coolant source90 may be any suitable housing containing a reservoir of coolant fluid “F”. Coolant fluid “F” may be any suitable fluid that can be used for cooling or buffering theprobe100, e.g., deionized water, or other suitable cooling medium. Coolant fluid “F” may have dielectric properties and may provide dielectric impedance buffering for theantenna assembly112. Coolant fluid “F” may be a conductive fluid, such as a saline solution, which may be delivered to the target tissue, e.g., to decrease impedance and allow increased power to be delivered to the target tissue. A coolant fluid “F” composition may vary depending upon desired cooling rates and the desired tissue impedance matching properties. Various fluids may be used, e.g., liquids including, but not limited to, water, saline, perfluorocarbon, such as the commercially available Fluorinert® perfluorocarbon liquid offered by Minnesota Mining and Manufacturing Company (3M), liquid chlorodifluoromethane, etc. In other variations, gases (such as nitrous oxide, nitrogen, carbon dioxide, etc.) may also be utilized as the cooling fluid. In yet another variation, a combination of liquids and/or gases, including, for example, those mentioned above, may be utilized as the coolant fluid “F”.

In the embodiment shown inFIG. 1, the fluid-movement device60 is provided in thefirst coolant path19 to move the coolant fluid “F” through thefirst coolant path19 and into, and out of, theprobe100. Fluid-movement device60 may include valves, pumps, power units, actuators, fittings, manifolds, etc. The position of the fluid-movement device60, e.g., in relation to thecoolant source90, may be varied from the configuration depicted inFIG. 1. Although thecoolant supply system11 shown inFIG. 1 includes a single, fluid-movement device60 located in thefirst coolant path19, various combinations of different numbers of fluid-movement devices, variedly-sized and variedly-spaced apart from each other, may be provided in thefirst coolant path19 and/or thesecond coolant path20.

In some embodiments, theprobe100 includes afeedline110 that couples theantenna assembly112 to a hub, e.g.,connection hub142, that provides electrical and/or coolant connections to theprobe100.Feedline110 may be formed from a suitable flexible, semi-rigid or rigid microwave conductive cable.Feedline110 may be constructed of a variety of electrically-conductive materials, e.g., copper, gold, or other conductive metals with similar conductivity values.Feedline110 may be made of stainless steel, which generally offers the strength required to puncture tissue and/or skin.

In some variations, theantenna assembly112 includes adistal radiating portion105 and aproximal radiating portion140. In some embodiments, a junction member (not shown), which is generally made of a dielectric material, couples theproximal radiating section140 and thedistal radiating section105. In some embodiments, the distal and proximal radiatingsections105,140 align at the junction member and are also supported by an inner conductor (not shown) that extends at least partially through thedistal radiating section105.

Antenna assembly112 may be provided with an end cap or tapered portion120, which may terminate in asharp tip123 to allow for insertion into tissue with minimal resistance. One example of a straight probe with a sharp tip that may be suitable for use as theenergy applicator100 is an EVIDENT™ microwave ablation probe offered by Covidien. The end cap or tapered portion120 may include other shapes, such as, for example, atip123 that is rounded, flat, square, hexagonal, or cylindroconical. End cap or tapered portion120 may be formed of a material having a high dielectric constant, and may be a trocar.

Sheath138 generally includes anouter jacket139 defining a lumen into which theantenna assembly112, or portion thereof, may be positioned. In some embodiments, thesheath138 is disposed over and encloses thefeedline110, theproximal radiating portion140 and thedistal radiating portion105, and may at least partially enclose the end cap or tapered portion120. Theouter jacket139 may be formed of any suitable material, such as, for example, polymeric or ceramic materials. Theouter jacket139 may be a water-cooled catheter formed of a material having low electrical conductivity.

In accordance with the embodiment shown inFIG. 1, acoolant chamber137 is defined by theouter jacket139 and the end cap or tapered portion120.Coolant chamber137 is disposed in fluid communication with theinlet fluid port179 and theoutlet fluid port177 and adapted to circulate coolant fluid “F” therethrough, and may include baffles, multiple lumens, flow restricting devices, or other structures that may redirect, concentrate, or disperse flow depending on their shape. Examples of coolant chamber embodiments are disclosed in commonly assigned U.S. patent application Ser. No. 12/350,292 filed on Jan. 8, 2009, entitled “CHOKED DIELECTRIC LOADED TIP DIPOLE MICROWAVE ANTENNA”, commonly assigned U.S. patent application Ser. No. 12/401,268 filed on Mar. 10, 2009, entitled “COOLED DIELECTRICALLY BUFFERED MICROWAVE DIPOLE ANTENNA”, and U.S. Pat. No. 7,311,703, entitled “DEVICES AND METHODS FOR COOLING MICROWAVE ANTENNAS”. The size and shape of thesheath138 and thecoolant chamber137 extending therethrough may be varied from the configuration depicted inFIG. 1.

During microwave ablation, e.g., using theelectrosurgical system10, theprobe100 is inserted into or placed adjacent to tissue and microwave energy is supplied thereto. Ultrasound or computed tomography (CT) guidance may be used to accurately guide theprobe100 into the area of tissue to be treated.Probe100 may be placed percutaneously or atop tissue, e.g., using conventional surgical techniques by surgical staff. A clinician may pre-determine the length of time that microwave energy is to be applied. Application duration may depend on many factors such as tumor size and location and whether the tumor was a secondary or primary cancer. The duration of microwave energy application using theprobe100 may depend on the progress of the heat distribution within the tissue area that is to be destroyed and/or the surrounding tissue. Single ormultiple probes100 may be used to provide ablations in short procedure times, e.g., a few seconds to minutes, to destroy cancerous cells in the target tissue region.

A plurality ofprobes100 may be placed in variously arranged configurations to substantially simultaneously ablate a target tissue region, making faster procedures possible.Multiple probes100 can be used to synergistically create a large ablation or to ablate separate sites simultaneously. Tissue ablation size and geometry is influenced by a variety of factors, such as the energy applicator design, number of energy applicators used simultaneously, time and wattage.

In operation, microwave energy having a wavelength, lambda (λ), is transmitted through theantenna assembly112, e.g., along the proximal anddistal radiating portions140,105, and radiated into the surrounding medium, e.g., tissue. The length of the antenna for efficient radiation may be dependent on the effective wavelength λ_effwhich is dependent upon the dielectric properties of the medium being radiated.Antenna assembly112, through which microwave energy is transmitted at a wavelength λ, may have differing effective wavelengths λ_effdepending upon the surrounding medium, e.g., liver tissue as opposed to breast tissue.

In some embodiments, theelectrosurgical system10 includes a first temperature sensor “TS₁” disposed within adistal radiating portion105 of theantenna assembly112. First temperature sensor “TS₁” may be disposed within or contacting the end cap or tapered portion120. It is to be understood that the first temperature sensor “TS₁” may be disposed at any suitable position to allow for the sensing of temperature.Processor unit82 may be electrically connected by atransmission line34 to the first temperature sensor “TS₁”. Sensed temperature signals indicative of a temperature of a medium in contact with the first temperature sensor “TS₁” may be utilized by theprocessor unit82 to control the flow of electrosurgical energy and/or the flow rate of coolant to attain the desired ablation.

Electrosurgical system10 may additionally, or alternatively, include a second temperature sensor “TS₂” disposed within theoutlet fluid port177 or otherwise associated with thethird branch176 of thehub body145.Processor unit82 may be electrically connected by atransmission line38 to the second temperature sensor “TS₂”. First temperature sensor “TS₁” and/or the second temperature sensor “TS₂” may be a thermocouple, thermistor, or other temperature sensing device. A plurality of sensors may be utilized including units extending outside thetip123 to measure temperatures at various locations in the proximity of thetip123.

FIG. 2 schematically illustrates an embodiment of a feedback control system, such as thefeedback control system14 ofFIG. 1, in accordance with the present disclosure, that includes theprocessor unit82 and amemory device8 in operable connection with theprocessor unit82. In some embodiments, thememory device8 may be associated with the electrosurgicalpower generating source28. In some embodiments, thememory device8 may be implemented as a storage device88 (shown inFIG. 3) integrated into the electrosurgicalpower generating source28. In some embodiments, thememory device8 may be implemented as an external device81 (shown inFIG. 3) communicatively-coupled to the electrosurgicalpower generating source28.

In some embodiments, theprocessor unit82 is communicatively-coupled to the flow-control device50, e.g., via a transmission line “L₅”, and may be communicatively-coupled to the fluid-movement device60, e.g., via a transmission line “L₆”. In some embodiments, theprocessor unit82 may be configured to control one or more operational parameters of the fluid-movement device60 to selectively adjust the fluid-flow rate in a fluid-flow path (e.g., first coolant path19) of thecoolant supply system11. In one non-limiting example, the fluid-movement device60 is implemented as a multi-speed pump, and theprocessor unit82 may be configured to vary the pump speed to selectively adjust the fluid-flow rate to attain a desired fluid-flow rate.

Processor unit82 may be configured to execute a series of instructions to control one or more operational parameters of the flow-control device50 based on determination of a desired fluid-flow rate using temperature data received from one or more temperature sensors, e.g., “TS₁”, “TS₂” through “TS_N”, where N is an integer. The temperature data may be transmitted via transmission lines “L₁”, “L₂” through “L_N” or wirelessly transmitted. One or more flow sensors, e.g., “FS₁”, “FS₂” through “FS_M”, where M is an integer, may additionally, or alternatively, be communicatively-coupled to theprocessor unit82, e.g., via transmission lines “L₃”, “L₄” through “L_M”. In some embodiments, signals indicative of the rate of fluid flow into and/or out of theprobe100 and/or conduit fluidly-coupled to theprobe100 received from one or more flow sensors “FS₁”, “FS₂” through “FS_M” may be used by theprocessor unit82 to determine a desired fluid-flow rate. In such embodiments, flow data may be used by theprocessor unit82 in conjunction with temperature data, or independently of temperature data, to determine a desired fluid-flow rate. The desired fluid-flow rate may be selected from a look-up table “T_X,Y” or determined by a computer algorithm stored within thememory device8.

In some embodiments, an analog signal that is proportional to the temperature detected by a temperature sensor, e.g., a thermocouple, may be taken as a voltage input that can be compared to a look-up table “T_X,Y” for temperature and fluid-flow rate, and a computer program and/or logic circuitry associated with theprocessor unit82 may be used to determine the needed duty cycle of the pulse width modulation (PWM) to control actuation of a valve (e.g., valve52) to attain the desired fluid-flow rate.Processor unit82 may be configured to execute a series of instructions such that the flow-control device50 and the fluid-movement device60 are cooperatively controlled by theprocessor unit82, e.g., based on determination of a desired fluid-flow rate using temperature data and/or flow data, to selectively adjust the fluid-flow rate in a fluid-flow path (e.g., first coolant path19) of thecoolant supply system11.

Feedback control system14 may be adapted to control the flow-control device50 to allow flow (e.g.,valve52 held open) for longer periods of time as the sensed temperature rises, and shorter periods of time as the sensed temperature falls.Electrosurgical system10 may be adapted to override PWM control of the flow-control device50 to hold thevalve52 open upon initial activation of theantenna assembly112. For this purpose, a timer may be utilized to prevent thecontrol device50 from operating for a predetermined time interval (e.g., about one minute) after theantenna assembly112 has been activated. In some embodiments, the predetermined time interval to override PWM control of the flow-control device50 may be varied depending on setting, e.g., time and power settings, provided by the user. In some embodiments, the electrosurgicalpower generating source28 may be adapted to perform a self-check routine that includes determination that the flow-control device50 is open before enabling energy delivery between the electrosurgicalpower generating source28 and theprobe100.

FIG. 3 is a block diagram of anelectrosurgical system300 including an embodiment of the electrosurgicalpower generating source28 ofFIG. 1 that includes agenerator module86 in operable communication with aprocessor unit82, auser interface121 communicatively-coupled to theprocessor unit82, and anactuator122 communicatively-coupled to theuser interface121.Actuator122 may be any suitable actuator, e.g., a footswitch, a handswitch, an orally-activated switch (e.g., a bite-activated switch and/or a breath-actuated switch), and the like.Probe100 is operably-coupled, e.g., viatransmission line16 shown inFIG. 1, to an energy output of thegenerator module86.User interface121 may include anindicator unit129 adapted to provide a perceptible sensory alert, which may be an audio, visual, such as an illuminated indicator (e.g., a single- or variably-colored LED indicator), or other sensory alarm.

In some embodiments, thegenerator module86 is configured to provide energy of about 915 MHz.Generator module86 may additionally, or alternatively, be configured to provide energy of about 2450 MHz (2.45 GHz) or about 5800 MHz (5.8 GHz). The present disclosure contemplates embodiments wherein thegenerator module86 is configured to generate a frequency other than about 915 MHz or about 2450 MHz or about 5800 MHz, and embodiments wherein thegenerator module86 is configured to generate variable frequency energy.

Processor unit82 according to various embodiments is programmed to enable a user, via theuser interface121, to preview operational characteristics of an energy-delivery device, such as, for example,probe100.Processor unit82 may include any type of computing device, computational circuit, or any type of processor or processing circuit capable of executing a series of instructions that are stored in a memory, e.g.,storage device88 orexternal device81.

In some embodiments, astorage device88 is operably-coupled to theprocessor82, and may include random-access memory (RAM), read-only memory (ROM), and/or non-volatile memory (e.g., NV-RAM, Flash, and disc-based storage).Storage device88 may include a set of program instructions executable on theprocessor unit82 for controlling the flow-control device50 based on determination of a desired fluid-flow rate in accordance with the present disclosure. Electrosurgicalpower generating source28 may include adata interface80 that is configured to provide a communications link to anexternal device81. In some embodiments, thedata interface80 may be any of a USB interface, a memory card slot (e.g., SD slot), and/or a network interface (e.g., 100BaseT Ethernet interface or an 802.11 “Wi-Fi” interface).External device81 may be any of a USB device (e.g., a memory stick), a memory card (e.g., an SD card), and/or a network-connected device (e.g., computer or server).

Electrosurgicalpower generating source28 may include adatabase84 that is configured to store and retrieve energy applicator data, e.g., parameters associated with one or energy applicators, and/or other data (e.g., one or more lookup tables “T_X,Y”).Database84 may also be maintained at least in part by data provided by anexternal device81 via thedata interface80, e.g., energy applicator data may be uploaded from theexternal device81 to thedatabase84 via thedata interface80.

FIG. 4 shows anelectrosurgical system410 according to an embodiment of the present disclosure that includes the electrosurgicalpower generating source28 and theprobe100 ofFIG. 1 and afeedback control system414 operably associated with acoolant supply system411 adapted to provide coolant fluid “F” to theprobe100. In some embodiments, thefeedback control system414 is adapted to provide a thermal-feedback-controlled rate of fluid flow to theprobe100.

Coolant supply system411 includes a substantially closed loop having afirst coolant path419 leading to theprobe100, asecond coolant path420 leading from theprobe100, and adiversion flow path421 disposed in fluid communication with thefirst coolant path419 and thesecond coolant path420.Coolant supply system411 generally includes thecoolant source90, fluid-movement device60, firstcoolant supply line66 leading from thecoolant source90 to the fluid-movement device60, and the firstcoolant return line95 leading to thecoolant source90 of thecoolant supply system11 ofFIG. 1.

In contrast to thecoolant supply system11 ofFIG. 1 that includes a flow-control device50 disposed in fluid communication with the first coolant path19 (fluidly-coupled to the inlet fluid port179) and a pressure-relief device40 disposed in fluid communication with thediversion flow path21, thecoolant supply system411 shown inFIG. 4 includes a flow-control device450 disposed in fluid communication with the diversion flow path421 (fluidly-coupled to the coolant source90). In the embodiment shown inFIG. 4, thecoolant path419 includes a secondcoolant supply line467 leading from the fluid-movement device60 to theinlet fluid port179 defined in theconnection hub142, and thediversion flow path421 includes a secondcoolant return line494 fluidly-coupled to the secondcoolant supply line467 and the firstcoolant return line95, wherein the flow-control device450 is disposed in fluid communication with the secondcoolant return line494.

Feedback control system414 includes a processor unit, e.g.,processor unit82 associated with the electrosurgicalpower generating source28, or a standalone processor (not shown), operably associated with the flow-control device450. Flow-control device450 may include any suitable device capable of regulating or controlling the rate of fluid flow passing though the flow-control device450. In the embodiment shown inFIG. 4, the flow-control device450 includes avalve452 including avalve body454 and anelectromechanical actuator456 operatively coupled to thevalve body454. In some embodiments, theactuator456 is operably associated with theprocessor unit82, e.g., via atransmission line432 or via wireless connection.

Processor unit82 may be configured to control the flow-control device450 by activating theactuator456 to selectively adjust the fluid-flow rate in thediversion flow path421 to effect a desired change in the fluid-flow rate in thefirst coolant path419 leading to theprobe100. In some embodiments, theprocessor unit82 may be configured to control the flow-control device450 by activating theactuator456 to selectively adjust the fluid-flow rate in thediversion flow path421 based on determination of a desired fluid-flow rate using data received from one or more temperature sensors (e.g., two sensors “TS₁” and “TS₂”) and/or data received from one or more flow sensors (e.g., one sensor “FS₁”).

In some embodiments, theelectrosurgical system410 includes one or more pressure sensors (e.g., pressure transducer70) disposed in fluid communication with one or more fluid-flow paths (e.g., first coolant path419) of thecoolant supply system411. In the embodiment shown inFIG. 4, thepressure transducer70 is disposed in fluid communication with thefirst coolant path419 located between the fluid-movement device60 and the flow-control device450.

FIG. 5 schematically illustrates afeedback control system514 according to an embodiment of the present disclosure that includes theprocessor unit82.Feedback control system514 is similar to thefeedback control system14 ofFIG. 2, except for the addition of pressure sensors “PS₁”, “PS₂” through “PS_K”, where K is an integer, and description of elements in common with thefeedback control system14 ofFIG. 2 is omitted in the interests of brevity.

Processor unit82 may be configured to enable the electrosurgicalpower generating source28 for activating theprobe100 based on determination that the pressure level of fluid in one or more fluid-flow paths of thecoolant supply system11 is above a predetermined threshold using pressure data received from one or more pressure sensors “PS₁”, “PS₂” through “PS_K”. The pressure data may be transmitted via transmission lines “L₈”, “L₉” through “L_K” or wirelessly transmitted.Processor unit82 may additionally, or alternatively, be configured to stop energy delivery from the electrosurgicalpower generating source28 to theprobe100 based on determination that the pressure level in one or more fluid-flow paths of thecoolant supply system11 is above a predetermined threshold using pressure data received from one or more pressure sensors “PS₁”, “PS₂” through “PS_K”.Processor unit82 may additionally, or alternatively, be configured to execute a series of instructions to control one or more operational parameters of an electrosurgicalpower generating source28 based on determination of whether the pressure level of fluid in theprobe100 and/or conduit fluidly-coupled to theprobe100 is above a predetermined threshold using pressure data received from one or more pressure sensors “PS₁”, “PS₂” through “PS_K”.

Hereinafter, methods of directing energy to tissue using a fluid-cooled antenna assembly in accordance with the present disclosure are described with reference toFIGS. 6 and 7. It is to be understood that the steps of the methods provided herein may be performed in combination and in a different order than presented herein without departing from the scope of the disclosure. Embodiments of the presently-disclosed methods of directing energy to tissue may be implemented as a computer process, a computing system or as an article of manufacture such as a pre-recorded disk or other similar computer program product or computer-readable media. The computer program product may be a non-transitory, computer-readable storage media, readable by a computer system and encoding a computer program of instructions for executing a computer process.

FIG. 6 is a flowchart illustrating a method of directing energy to tissue using a fluid-cooled antenna assembly according to an embodiment of the present disclosure. Instep610, anenergy applicator100 is provided. Theenergy applicator100 includes anantenna assembly112 and ahub142 providing one or more coolant connections (e.g.,inlet fluid port179 shown inFIG. 1) to theenergy applicator100.

Instep620, a coolant supply system11 (orcoolant supply system411 shown inFIG. 4) is provided. Thecoolant supply11 includes a fluid-flow path19 fluidly-coupled to thehub142 for providing fluid flow to theenergy applicator100. In some embodiments, thefirst coolant path19 includes a firstcoolant supply line66 leading from acoolant source90 to a fluid-movement device60, a secondcoolant supply line67 leading from the fluid-movement device60 to a flow-control device50, and a thirdcoolant supply line68 leading from the flow-control device50 to theinlet fluid port179.

Coolant source90 may be any suitable housing containing a reservoir of coolant fluid “F”. Coolant fluid “F” may be any suitable fluid that can be used for cooling or buffering theenergy applicator100, e.g., deionized water, or other suitable cooling medium. Coolant fluid “F” may have dielectric properties and may provide dielectric impedance buffering for theantenna assembly112.

Instep630, theenergy applicator100 is positioned in tissue for the delivery of energy to tissue when theantenna assembly112 is energized. Theenergy applicator100 may be inserted directly into tissue, inserted through a lumen, e.g., a vein, needle, endoscope or catheter, placed into the body during surgery by a clinician, or positioned in the body by other suitable methods. Theenergy applicator100 may be configured to operate with a directional radiation pattern.

Electrosurgical energy may be transmitted from anenergy source28 through theantenna assembly112 to tissue. Theenergy source28 may be any suitable electrosurgical generator for generating an output signal. In some embodiments, theenergy source28 is a microwave energy source, and may be configured to provide microwave energy at an operational frequency from about 300 MHz to about 10 GHz. In some embodiments, theenergy source28 supplies power having a selected phase, amplitude and frequency.

Instep640, a thermal-feedback-controlled rate of fluid flow is provided to theantenna assembly112 when energized, using afeedback control system14 operably-coupled to a flow-control device50 disposed in the fluid-flow path19 leading to theenergy applicator100.

FIG. 7 is a flowchart illustrating a method of directing energy to tissue using a fluid-cooled antenna assembly according to an embodiment of the present disclosure. Instep710, anenergy applicator100 is provided. Theenergy applicator100 includes anantenna assembly112 and acoolant chamber137 adapted to circulate coolant fluid “F” around at least a portion of theantenna assembly112.

Instep720, a coolant supply system that is adapted to provide coolant fluid “F” to theenergy applicator100 is provided. Theenergy applicator100 may be used in conjunction with coolant supply systems in various configurations. Thecoolant chamber137 of theenergy applicator100 may be fluidly-coupled to acoolant supply system11 according to an embodiment shown inFIG. 1 that includes a flow-control device50 disposed in fluid communication with a first coolant path19 (e.g., fluidly-coupled to theenergy applicator100 to provide fluid flow from acoolant source90 to the energy applicator100).

Alternatively, thecoolant chamber137 may be fluidly-coupled to acoolant supply system411 according to an embodiment shown inFIG. 4 that includes a flow-control device450 disposed in fluid communication with athird coolant path421 disposed in fluid communication with a first coolant path419 (e.g., fluidly-coupled to theenergy applicator100 to provide fluid flow from acoolant source90 to the energy applicator100) and a second coolant path420 (e.g., fluidly-coupled to theenergy applicator100 to provide fluid flow from theenergy applicator100 to the coolant source90).

Instep730, theenergy applicator100 is positioned in tissue for the delivery of energy to tissue when theantenna assembly112 is energized. Theenergy applicator100 may be inserted into or placed adjacent to tissue to be treated.

Instep740, a feedback control system14 (or414) including aprocessor unit82 communicatively-coupled to one or more temperature sensors, e.g., one temperature sensor “TS₁”, associated with theenergy applicator100 is used to provide a thermal-feedback-controlled rate of fluid flow to theantenna assembly112 when energized.Processor unit82 may be configured to control a flow-control device50 (or450) associated with the coolant supply system11 (or411) based on determination of a desired fluid-flow rate using one or more electrical signals outputted from the one or more temperature sensors “TS₁”. Feedback control system14 (or414) may utilize data “D” (e.g., data representative of a mapping of temperature data to settings for properly adjusting one or more operational parameters of the flow-control device50 (or450) to achieve a desired temperature and/or desired ablation) stored in a look-up table “T_X,Y”, or other data structure, to determine the desired fluid-flow rate.

In some embodiments, theprocessor unit82 is communicatively-coupled to one ormore pressure sensors70 disposed in fluid communication with one or more fluid-flow paths (e.g., first coolant path19) of the coolant supply system11 (or411).Processor unit82 may be configured to enable anelectrosurgical generator28 for activating theenergy applicator100 based on determination that a sensed pressure level in the one or more fluid-flow paths is above a predetermined threshold using at least one electrical signal outputted from the one ormore pressure sensors70.

Processor unit82 may additionally, or alternatively, be configured to control one or more operating parameters associated with theelectrosurgical generator28 based on determination that a sensed pressure level in the one or more fluid-flow paths (e.g., first coolant path19) is below a predetermined threshold using at least one electrical signal outputted from the one ormore pressure sensors70. Examples of operating parameters associated with the electrosurgicalpower generating source28 include without limitation temperature, impedance, power, current, voltage, mode of operation, and duration of application of electromagnetic energy.

In some embodiments, thecoolant supply system11 includes a fluid-movement device60 disposed in fluid communication with thefirst coolant path19, and may include a second coolant path20 (e.g., fluidly-coupled to theenergy applicator100 to allow fluid flow to return to the coolant source90) and athird coolant path21 disposed in fluid communication with thefirst coolant path19 and thesecond coolant path20. A pressure-relief device40 may be disposed in fluid communication with thethird coolant path21 and may allow the fluid-movement device60 to run at a substantially constant speed and/or under a near-constant load (head pressure) regardless of the selective adjustment of the fluid-flow rate in thefirst coolant path19

The above-described systems for thermal-feedback-controlled rate of fluid flow to electrosurgical devices and methods of directing energy to tissue using a fluid-cooled antenna assembly may be used in conjunction with a variety of electrosurgical devices adapted for treating tissue. Embodiments may be used in conjunction with electrosurgical devices adapted to direct energy to tissue, such as ablation probes, e.g., placed percutaneously or surgically, and/or ablation devices suitable for use in surface ablation applications.

The above-described systems including a feedback control system adapted to provide a thermal-feedback-controlled rate of fluid flow to an energy applicator disposed in fluid communication with a coolant supply system may be suitable for a variety of uses and applications, including medical procedures, e.g., tissue ablation, resection, cautery, vascular thrombosis, treatment of cardiac arrhythmias and dysrhythmias, electrosurgery, etc.

Although embodiments have been described in detail with reference to the accompanying drawings for the purpose of illustration and description, it is to be understood that the inventive processes and apparatus are not to be construed as limited thereby. It will be apparent to those of ordinary skill in the art that various modifications to the foregoing embodiments may be made without departing from the scope of the disclosure.

Claims (13)

What is claimed is:

1. A method of directing energy to tissue by using a fluid-cooled antenna assembly of an energy applicator, the method comprising:

connecting the energy applicator to a hub, the hub coupled to a coolant supply system for providing fluid to the antenna assembly of the energy applicator, the coolant supply system having a coolant source, a first coolant supply line, a second coolant supply line, and a third coolant supply line in fluid communication with the coolant source, the first coolant supply line connected between the coolant source and a fluid-movement device, the second coolant supply line directly connected between a pressure transducer and the fluid-movement device, and the third coolant supply line directly connected between a flow-control device and the antenna assembly;

positioning the energy applicator in tissue;

activating the energy applicator via an electrosurgical generator;

measuring a temperature of the fluid in the antenna assembly;

controlling a thermal-feedback-controlled rate of fluid flow based on the measured temperature of the fluid in the antenna assembly;

providing fluid to the antenna assembly at the thermal-feedback-controlled rate of fluid flow using a feedback control system including the flow-control device, the flow control device including a valve and an electro-mechanical actuator, and the feedback control system including a processor unit; and

connecting the pressure transducer to the valve, the pressure transducer disposed within the coolant supply system;

wherein the pressure transducer outputs a signal at a pressure below a burst pressure of a pressure relief valve to indicate to the electrosurgical generator that the fluid-cooled antenna assembly has coolant flowing therethrough and wherein the processor unit triggers a shut-off of the electrosurgical generator based on pressure levels of the coolant in the fluid-cooled antenna assembly; and

wherein the processor unit outputs a signal indicative of an error code if a predetermined time elapses between energy delivery to the fluid-cooled antenna assembly and detection of the signal outputted by the pressure transducer.

2. The method of directing energy to tissue by using the fluid-cooled antenna assembly ofclaim 1, wherein the providing step further includes controlling the flow-control device by activating the electro-mechanical actuator to selectively adjust the rate of fluid-flow in response to at least one electrical signal received from at least one temperature sensor which performs the measuring of the temperature of the fluid in the antenna assembly.

3. The method of directing energy to tissue by using the fluid-cooled antenna assembly ofclaim 2, wherein the at least one temperature sensor is disposed within a distal radiating portion of the antenna assembly.

4. The method of directing energy to tissue by using the fluid-cooled antenna assembly ofclaim 2, wherein the at least one temperature sensor is disposed within a fluid return port defined in the hub.

5. The method of directing energy to tissue by using the fluid-cooled antenna assembly ofclaim 2, wherein the processor unit is incorporated within the electrosurgical generator and communicatively-coupled to the electro-mechanical actuator of the flow-control device.

6. The method of directing energy to tissue by using the fluid-cooled antenna assembly ofclaim 5, wherein the processor unit is further communicatively-coupled to at least one flow sensor.

7. The method of directing energy to tissue by using the fluid-cooled antenna assembly ofclaim 1, wherein the electro-mechanical actuator is controlled by pulse width modulation (PWM) techniques.

8. A method of directing energy to tissue by using a fluid-cooled antenna assembly of an energy applicator, the method comprising:

connecting the energy applicator to a coolant supply system adapted to circulate coolant fluid around at least a portion of the antenna assembly, the coolant supply system having a coolant source, a first coolant supply line, a second coolant supply line, and a third coolant supply line in fluid communication with the coolant source, the first coolant supply line connected between the coolant source and a fluid-movement device, the second coolant supply line directly connected between a pressure transducer and the fluid-movement device, and the third coolant supply line directly connected between a flow-control device and the antenna assembly;

positioning the energy applicator in tissue;

activating the energy applicator via an electrosurgical generator;

measuring a temperature of the coolant fluid in the antenna assembly;

controlling a thermal-feedback-controlled rate of fluid flow based on the measured temperature of the coolant fluid in the antenna assembly;

providing coolant fluid to the antenna assembly at the thermal-feedback-controlled rate of fluid flow using a feedback control system including a processor unit configured to control the flow-control device, the flow control device having a valve and an electro-mechanical actuator by activating the electro-mechanical actuator to selectively adjust the rate of fluid-flow in response to at least one electrical signal received from at least one temperature sensor associated with the energy applicator; and

connecting a pressure transducer with to the valve, the pressure transducer disposed within the coolant supply system;

wherein the pressure transducer outputs a signal at a pressure below a burst pressure of a pressure relief valve to indicate to the electrosurgical generator that the fluid-cooled antenna assembly has coolant flowing therethrough and wherein the processor unit triggers a shut-off of the electrosurgical generator based on pressure levels of the coolant in the fluid-cooled antenna assembly; and

wherein the processor unit outputs a signal indicative of an error code if a predetermined time elapses between energy delivery to the fluid-cooled antenna assembly and detection of the signal outputted by the pressure transducer.

9. The method of directing energy to tissue by using the fluid-cooled antenna assembly ofclaim 8, wherein the electro-mechanical actuator is controlled by pulse width modulation (PWM) techniques.

10. The method of directing energy to tissue by using the fluid-cooled antenna assembly ofclaim 8, wherein the pressure transducer allows the fluid-movement device to operate under a near-constant load.

11. The method of directing energy to tissue by using the fluid-cooled antenna assembly ofclaim 8, wherein the coolant supply system includes a closed loop configuration such that coolant fluid does not contact tissue, the closed loop configuration having a first coolant path leading to the antenna assembly from the coolant source and a second coolant path leading from the antenna assembly to the coolant source, the first coolant path formed by the first, second, and third coolant supply lines.

12. The method of directing energy to tissue by using the fluid-cooled antenna assembly ofclaim 8, wherein the processor unit is further configured to control at least one operating parameter associated with the electrosurgical generator.

13. The method of directing energy to tissue by using the fluid-cooled antenna assembly ofclaim 12, wherein the at least one operating parameter associated with the electrosurgical generator is selected from the group consisting of temperature, impedance, power, current, voltage, mode of operation, and duration of application of electromagnetic energy.

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